Reactors having cores and coils surrounded by magnetic shell



y 2, 1963 L. STOKKELAND ETAL 3,391,366

REACTORS HAVING CORES AND COILS SURROUNDED BY MAGNETIC SHELL Filed Aug. 22 1966 F|G.l 2 FIG.2 H64 INVENTORS LEIDULV STOKKELAND, TRYGVE K. BRUNE, BIRGER HATLEBAKK 19 19W, WM

ORNEYS United States Patent REACTORS HAVING CORES AND COILS SUR- ROUNDED BY MAGNETIC SHELL Leidulv Stoklreland, Trygvc K. Brune, and Birger Hatlebakk, all of Molde, Norway Continuation-impart of application Ser. No. 320,602, Oct. 24, 1963. This application Aug. 23, 1966, Ser. No. 574,397

Claims priority, application Norway, Oct. 27, 1962,

2 Claims. (a. 33683) ABSTRACT OF THE DISCLOSURE The present application is a continuation-in-part application of our earlier filed application Ser. No. 320,602, filed Oct. 24, 1966, now abandoned.

The present invention relates to cores for reactors for electric discharge lamps, e.g., lamps of tubular shape for luminous purposes. The invention more particularly relates to a core designed to carry two windings arranged symmetrically in relation to the central longitudinal axis of the core, or in other words, so that the windings will be located in a side-by-side relationship on a common core with the axis of the windings located transversally to the longitudinal axis of the core.

It is well known to use reactors or choke coils wound on cores, for example, of E shape, in which the windings are arranged on the outer legs of the E-shape core and in which the legs of the core are magnetically interconnected by means of sheet iron or the windings are located on the web of the E-shape core between the legs.

The object of the present invention is to provide a core for reactors for discharge lamps, which has a substantial attenuation or suppression of radio interference or noise.

It has been found that the attenuation of radio noise from discharge lamps is substantially improved if the reactor consists of two divided, symmetrical windings instead of a single winding. It has further been found that better results are obtained as to the suppression of noise if the divided symmetrical windings are placed on a single core rather than on two separate cores.

The best results of the suppression of radio disturbances originating from electric discharge lamps are thus obtained, according to the invention, by using a core in which there are formed two parallel grooves, preferably having a trapezoidal cross section, for the disposal therein of two separate windings. The core, according to the invention, is designed in such a way that the two grooves are formed in a sheet iron package of the core as well as in end pieces and are symmetrical about the longitudinal axis of the core as well as symmetrical to the transverse axis of the choke coil or its winding axis. It is also of main importance that the two grooves are separated by means of a strong partition, which is formed by the core or in some other way.

Another important feature of the core according to the invention is that the cross-sectional area of the air gap 3,391,366 Patented July 2, 1968 ice is larger than the cross section of the core thus substantially reducing mechanical humming.

The means for accomplishing the foregoing objects and other advantages, which will be apparent to those skilled in the art, are set forth in the following specification and claims and are illustrated in the accompanying drawings dealing with a basic embodiment of the present invention. Reference is made now to the drawings in which:

FIG. 1 is a front elevation, partially in section, of a reactor utilizing the inventive core;

FIG. 2 is a partial sectional view of the reactor taken along the line 22 of FIG. 1;

FIG. 3 is a transverse sectional view of the reactor taken along the line 33 of FIG. 1;

FIG. 4 is a wiring diagram of a typical circuit including the reactor; and

'FIG. 5 is a perspective view of the core.

Refering to FIG. 1, the reactor 1 consists of a core 2 made from sheet iron and provided with end pieces 4. The core is surrounded by a sheet iron shell Two symmetrical grooves 5' and 5" are provided in the end pieces 4 (see FIG. 1) as well as in the core 2 itself (see FIG. 2). The symmetrical grooves 5' and 5" preferably have a trapezoidal cross section and serve to take up win-dings 6 and 6", respectively. The grooves 5 and 5" are parallel and traverse the periphery of the core and the end pieces. By this coil arrangement, the windings 6 and 6" will be located in the trapezoidal grooves 5' and 5", respectively, in a side-by-side relationship, symmetrically with the longitudinal axis of the core 2. The two trapezoidal grooves serve as forms for the winding and are separated by a rigid central web or partition 7 constituting an electrical insulation point between the two windings. Any suitable insulating means well-known to those skilled in the art may be included at this point to separate the windings from each other and the core. The end pieces 4 are held in place on the core by the windings passing through the grooves therein.

The air gap 8 between the core 2 and the shell 3, according to the invention, has a crosssectional area greater than the cross section of the core 2, thus substantially reducing the mechanical humming of the reactor when in use.

Referring to FIG. 5 showing the core in perspective, it is apparent that the cross section of the core C is smaller than that of the air gap L. For the sheet iron of the inventive core, the magnetic flux should not exceed a certain value, for instance, 10,000 gauss. Since the magnetic flux through the air gap is the same as that through the core cross section, the magnetic flux density in the air gap must be smaller than the magnetic fiux density in the iron core as defined by the proportion C/ L. The magnetic flux density in the air gap is decreased in relation to that in the iron core cross section because the magnetic flux density in the air gap is reduced as explained above.

The magnetic force between shell and core according to the equation (1) FocB 'A will decrease because of the greater air gap area.

The relation between B and A is given by (2) Botdivided coil is achieved. It is also possible to start and complete the windings on the outside of each groove. The connections are provided in such a way that each coil half has corresponding terminals at each end of the core, as will appear from FIGS. 1 and 4. The terminals are designated 9 and 12 for one winding and 10 and 11 for the other winding, respectively. This arrangement of the terminals avoids crossing of the leads or wires of the drawings, both within each coil half and between each coil half, to thereby prevent short circuiting.

In FIG. 4 there is shown a wiring diagram for a typical circuit using the reactor with symmetrical windings according to the invention. The lamp is shown at 13 with its associated capacitance indicated by '14. It is clear how the windings are arranged on a common core and are completely independent and separately connected in the circuit.

It should be noted that the invention is not limited to the trapezoidally formed cross section shown and described above as an embodiment, but the two symmetrical winding grooves in the core may also have other suitable forms without departing from the spirit of the invention.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore to be embraced herein.

What is claimed is:

1. A reactor for electric discharge lamps generally of a tubular shape and for illuminating purposes comprising a parallelepiped core, said core comprising a plurality of adjacent plates of ferromagnetic material laminated together, end pieces attached to each end of said core, two spaced parallel grooves traversing the periphery of said core, said end pieces being shaped to continue the grooves about the ends of said core, two windings, each winding being wound in one of said grooves, a portion of said core projecting 'between said parallel grooves to separate said windings, insulating means electrically insulating said windings from said core and from each other, said windings being symmetrical about the longitudinal and transverse axes of said core, said windings being Wound in opposite directions with the input and output leads of each said winding appearing at opposite ends of said core thus avoiding crossing of the windings and their input and output leads, a shell comprising a plurality of iron sheets laminated together and encompassing and enclosing said core but being spaced therefrom, the cross-sectional area of an air gap formed between said core and said shell being larger than the cross section of said core.

2. A reactor for electric discharge lamps according to claim 1 in which said grooves have a trapezoidal cross section.

References Cited UNITED STATES PATENTS 1,417,710 5/1922 Ballman 336-83 X 1,529,570 3/1925 Bethke "336- 83 X 3,071,743 1/1963 La Patka et a1. 336-208 X 3,078,429 2/ 1963 Weisner 33683 3,146,420 8/1964 Knobel 336- 83 LARAMIE E. ASKIN, Primary Examiner. T. J. KOZ'MA, Assistant Examiner. 

